The typical ultraviolet-visible (UV-Vis) molecular absorption spectroscopic method requires the reaction of an analyte with a colorimetric reagent. The resulting solution is transferred into a cuvette and the cuvette placed into a spectrophotometer for the analysis of the analyte in the solution. The cuvette may be characterized as a removable sample reservoir of the spectrophotometer. This methodology is difficult to automate, restricts the path length, and the optical system and electronics are large and expensive. The instrumentation is not optimized for long-term use in the field.
A removable sample reservoir with detectors and sources embedded in the the walls of a cell containing the removable sample reservoir was disclosed in U.S. Pat. No. 5,107,133 by Klainer. The disclosure does simplify the optics and electronics over the typical UV-Vis methods, however, the method has a removable reservoir. The invention is not optimized for the automation of the sampling, sample preparation and analysis.
A chemical reservoir sensor for molecular absorption and florescence was disclosed in U.S. Pat. No. 5,116,756 by Klainer et al. The invention sought to eliminate the need for fiber optics and used excitation sources and detectors embedded in the walls of the chemical reservoir, The chemical sensing reagent was contained within the body of the chemical reservoir and the analyte introduced into the reagent. The analyte was introduced into the chemical reservoir using a variety of techniques including permeable membranes embedded in the walls of the sample reservoir.
The invention presented in this disclosure uses fittings containing the excitation source or detector or both. Fiber optics are used to transmit light from the excitation source into the interior of the sample cell. Fiber optics are used to transmit light from the interior of the sample chamber to the detector. The sample reservoir is not removal and the sensing reagent does not reside in the sample reservoir.
There are several commercially-available fiber optic fittings for connecting fiber optics to sample curvettes for spectroscopic analysis. However, the terminal end of the fiber optic is conducted to an excitation source or a detector, or grating spectrometer, using a second fiber optic fitting. This invention does not transmit light through the optical fitting. The optical fittings described in this invention has the excitation source or detector located within the fittings. The fittings transmit electrical signals, not optical signals, to external instrument components, i.e. amplifers, etc. The second major difference is the terminal end of the fiber optic fitting in this disclosure is actually placed into the solution being analyzed. The commercially-available fiber optic fittings usually terminate at the outer wall of a cuvette. Several advantages to this design include the mininaturization of the entire system, the path length may be adjusted and the problems associated with bending fiberoptics in areas of limited space are eliminated.